1. Field of the Invention
The present invention relates to a semiconductor device, and in particular to a semiconductor device that incorporates a voltage generating circuit, converting an external power-supply potential supplied from an external power-supply into an internal power-supply potential which is to be used for driving an internal circuit.
2. Description of the Background Art
In a device including a group of internal circuits driven at various potential levels, such as a semiconductor device, a voltage generating circuit is used, for converting an external power-supply potential supplied from an external power-supply into an internal power-supply potential of a desired potential level. Such a voltage generating circuit includes a socalled VDC (Voltage Down Converter) or the like.
FIG. 14 is a schematic block diagram showing a configuration of a voltage generating circuit 500 commonly used for generation of an internal power potential within a semiconductor device.
Referring to FIG. 14, voltage generating circuit 500 includes a VREF generating circuit 510 receiving an external power-supply potential VDD from an external power-supply line 505 to generate a reference potential signal VREF corresponding to a set value of the internal power-supply potential, and a VDC 520 generating an internal power-supply potential Vcc to an internal power-supply line 525.
VDC 520 compares a potential level of internal power-supply line 525 to that of reference potential signal VREF, and if the potential level of internal power-supply line 525 is lower than that of reference potential signal VREF, VDC 520 supplies current from external power-supply line 505 to internal power-supply line 525 in an attempt to hold internal power-supply potential Vcc at a target level.
Therefore, when an external power-supply is turned on and external power-supply potential rises at external power-supply line 505, the potential level of reference potential signal VREF rises, and then internal power-supply potential Vcc is controlled by VDC 520 based on reference potential signal VREF.
Thus, in voltage generating circuit 500, when the external power-supply is turned on, the external power-supply potential, reference potential signal VREF and internal power-supply potential Vcc are activated in this order. Setting accuracy of internal power-supply potential Vcc, which is controlled by voltage generating circuit 500, is greatly affected by the setting accuracy of reference potential signal VREF, so that a configuration in which reference potential signal VREF is generated stepwise is also used, in order to avoid transient overshoot and so forth and to more stably generate internal power-supply potential Vcc.
However, in a semiconductor device, time period from activation of the external power-supply to actual operation of an internal circuit must satisfy a standard value defined by a specification. Thus, when the external power-supply is turned on (hereinafter also referred to as xe2x80x9cat the time of power onxe2x80x9d), at which transient variation in potential tends to occur, stable generation of reference potential signal VREF is required, while speed-up of rising of internal power-supply potential Vcc is also required.
Monitoring potential level of the internal power-supply line, if the potential level of internal power-supply potential Vcc is not higher than a predetermined value, an operational speed of VDC may possibly be increased to be higher than usual. However, at an initial state, i.e., at the time of power on, the potential level of each internal node is in a transient state. Therefore, there arises a problem that which internal node is to be compared, for its potential level, with internal power-supply potential Vcc, to switch the operational speed of VDC.
It is an object of the present invention to provide a configuration of a semiconductor device, in which an internal power-supply potential used in an internal circuit can be generated at a high speed at the time of power on.
It is another object of the present invention to provide a configuration of a semiconductor device, in which rising speed of an internal power-supply potential at the time of power on can be easily selected in a manufacturing process.
According to one aspect of the present invention, a semiconductor device, supplied, for operation, with a first external power-supply potential from a first external power-supply, includes an external power-supply line, a voltage generating circuit and an internal circuit. The external power-supply line transmits the first external power-supply potential. The voltage generating circuit converts the first external power-supply potential received from the external power-supply line into an internal power-supply potential to be supplied to an internal power-supply line. The internal circuit receives the internal power-supply potential from the internal power-supply line, for operation. The voltage generating circuit includes a reference potential generating unit receiving the first external power-supply potential from the external power-supply line to generate a reference potential signal in accordance with a set potential level of the internal power-supply potential at an intermediate node, a voltage converting circuit supplying current, in accordance with a difference between potential levels of the internal power-supply line and the first intermediate node, from the external power-supply line to the internal power-supply line, a first current supply circuit supplying a first operational current to the voltage converting circuit during an activation period of a first control signal, and a first activation control circuit activating the first control signal for the period from activation of the first external power-supply until the potential level of the internal power-supply line reaches a predetermined level. The first activation control circuit detects the activation of the first external power-supply by comparing potential level of a first reference node transmitting a first potential with that of the internal power-supply line. The first reference node is electrically separated from a node affecting a potential level of the reference potential signal.
According to another aspect of the present invention, a semiconductor device, supplied with a first external power-supply potential from a first external power-supply for operation, includes an external power-supply line, a plurality of voltage generating circuits and a plurality of internal circuits. The external power-supply line supplies the first external power-supply potential. The plurality of voltage generating circuits convert the first external power-supply potential received from the external power-supply line into a plurality of internal power-supply potentials respectively. The plurality of internal circuits respectively receive the plurality of internal power-supply potentials from the plurality of voltage generating circuits. Each of the voltage generating circuits includes an internal power-supply line outputting a corresponding one of the plurality of internal power-supply potentials, a reference potential generating unit receiving the first external power-supply potential from the external power-supply line, to generate a reference potential signal in accordance with a set potential level of the corresponding one of internal power-supply potentials, a voltage converting circuit supplying current in accordance with a difference between potential levels of the internal power-supply line and a first intermediate node from the external power-supply line to the internal power-supply line, a voltage converting circuit supplying current in accordance with a difference between potential levels of the internal power-supply line and the first intermediate node, and a first current-supply circuit supplying a first operational current to the voltage converting circuit in response to an activation of a first control signal. One of the plurality of voltage generating circuits includes a first activation control circuit activating the first control signal, for a period from activation of the first external power-supply until a potential level of the internal power-supply line corresponding to any one of the plurality of voltage generating circuits reaches a predetermined potential level. The first activation control circuit detects the activation of the first external power-supply by comparing a potential level of a first reference transmitting a first potential to that of the internal power-supply line corresponding to another one of the plurality of voltage generating circuits. The first reference node is electrically separated from a node affecting a potential level of the reference potential signal.
According to a further aspect of the present invention, a semiconductor device supplied with first and second external power-supply potentials respectively from first and second external power-supply, for operation, includes a first external power-supply line, a second external power-supply line, a voltage generating circuit, an internal circuit, and first, second and third metal interconnections. The first external power-supply line supplies the first external power-supply potential. The second external power-supply line supplies the second external power-supply potential. The voltage generating circuit converts the first external power-supply potential received from the first external power-supply line into an internal power-supply potential to be supplied to an internal power-supply line. The internal circuit receives the internal supply potential, for operation. The voltage generating circuit includes a reference potential generating unit receiving the first external power-supply potential from the first external power-supply line, for generating a reference potential signal in accordance with a set potential level of the internal power-supply potential at a first intermediate node, a voltage converting circuit supplying current in accordance with a difference between potential levels of the internal power-supply line and the first intermediate node, from the first external power-supply line to the internal power-supply line, a first current-supply circuit supplying a first operational current to the voltage converting circuit during an activation period of a first control signal, and a first activation control circuit activating the first control signal, for a period from activation of the first external power-supply until a potential level of the internal power-supply line reaches a predetermined level. The first activation control circuit detects the activation of the first external power-supply, by comparing a potential level of a first reference node to that of the internal power-supply line. The first, second and third metal interconnections are formed on a same metal interconnection layer and electrically coupled to the first reference node, the first intermediate node and the second external power-supply line, respectively. The first metal interconnection and one of the second and third metal interconnections are electrically coupled on the metal interconnection layer.
Therefore, a main advantage of the present invention is that, at the time of activation of the first external power-supply, rising speed of the internal power-supply potential can be increased by avoiding the temporary decrease of the potential level of the reference potential signal, caused by the operation of the first activation control circuit for rapidly charging the internal power-supply line generating the internal power-supply potential.
Moreover, in a semiconductor device generating a plurality of internal power-supply potentials, the first activation control circuit for rapidly charging the internal power-supply line at the time of activation of the external power-supply can be shared across a plurality of voltage generating circuits, so that circuit area can be reduced.
Furthermore, at the time of manufacturing semiconductor device, it is possible, by switching a metal mask for forming a metal interconnection layer, to select whether internal power-supply potential is generated based on a plurality of external power-supplies, giving priority to the rising speed, or based on a single external power-supply, giving priority to the operational stability.